\Fer"rule\ (? or ?; 277), n. [Formerly verrel, F.
virole, fr. L. viriola little bracelet, dim. of viriae, pl.,
bracelets; prob. akin to viere to twist, weave, and E. withe.
The spelling with f is due to confusion with L. ferrum iron.]
1. A ring or cap of metal put round a cane, tool, handle, or
   other similar object, to strengthen it, or prevent
   splitting and wearing.
2. (Steam Boilers) A bushing for expanding the end of a flue
   to fasten it tightly in the tube plate, or for partly
   filling up its mouth.